Baked enamel garage doors

Greetings,

In '97 I had a couple new steel garage doors installed.
Baked enamel, dark brown in color. They take the full
brunt of the morning sun here in the midwest. I probably
shoulda got white so they'd absorb less of the sun's heat.

The gloss on the baked enamel is mostly gone, they look
kinda dingy.

Is there anything I can to to preserve the baked enamel
finish?

TIA,
Puddin'

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